Gunfire control system



July 2, 1946.

Filed Jan.

J. F. PETERS GUNFIRE CONTROL SYSTEM s, 1941 5 sheets-sheet 1 ATTO R N EYJuly 2, 1946. 1 F, PETERS V2,403,117

GUNFIRE CONTROL SYSTEM Filed Jan. 8, 1941 5 Sheets-Sheet 2 4 2am-.Syed252, 2s 29 f6 Range Yards ATTORNEY July 2, 1946.

J. F. PETERS GUNFIRE CONTROL SYSTEM Filed Jan. 8, 1941 5 Sheets-Shed'I 3Jblm F' Peters.

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.R O T T July 2, 1946. J, F, PETERS 2,403,117

GUNFIRE CONTROL SYSTEM IIIIllllllflllllllllllllf E INVENTOR WITNESSESZJohn F -eers mw BY July 2, 1946. J. F. PETERS GUNFIRE CONTROL SYSTEMFiled Jan. 8, 1941 5 Sheets-Sheet 5 Patented July 2, 1946 2,403,117GUNFIRE CONTROL SYSTEM John F. Peters, Edgewood, Pa., assignor toWestinghouse Electric Corporation,

a corporation of Pennsylvania East Pittsburgh,

Application January 8, 1941, Serial No. 373,699

27 Claims.

My invention relates to a gunnre control system which may be adapted tostationary guns on the ground, but which is more specifically useful forguns mounted on aircraft, that is, guns in night. My inventionspecincally relates to means for automatically compensating for variouserrors which are introduced when a gun mounted on an airplane in flightis nred at a moving target such as another airplane in flight, whicherrors are aected by azimuth, elevation and range of the target, andwhich errors include ballistic errors, errors due to time of night ofthe projectile in determining lead angles and errors due to air speedand altitude of the plane in which the gun is mounted.

An object of my invention is to provide a gunfire control systemsuitable for use on an airplane which will automatically compensate forall errors in the angular positioning of the gun introduced when suchgun is nred at a moving target such as another airplane and which willprovide the proper angle of lead when aiming at a moving target.

A more specific object of my invention is to provide a system includinga pair of threedimensional cams which cams are moved lengthwise androtated in directions corresponding respectively to elevation andazimuth movements of the gun, each having a tracer, which tracers areinterconnected by a suitable linkage means including a variably pivotedlever so that the ultimate output of the summation of effects of the twotracers as modified by the variable pivot will give corrections for anypoint in the volume of a sphere. The shapes of such cams may be made inaccordance with precalculated ballistic data, so that corrections may bemade for errors resulting from projectile ballistics, time of night ofthe projectile, and the air speed and altitude at which the projectileis nred.

Another object of my invention is to provide a suitable follow-up systemby which a gun may be moved in accordance with piloting movements of thesight (or of a piloting member which controls the movements of the sightand gun) together with means forl automatically introducing in saidfollow-up system deviations between the gun and sight, so that onlysubstantial rather than exact follow-up occurs in order to compensatefor various errors which are introduced such as ballistic errors, timeof night errors, etc.

Other objects and advantages will become more apparent from a study ofthe following specincation when considered in conjunction with theaccompanying drawings, in which:

2 Fig. la is a three coordinate vector diagram illustrating afundamenta1 principle of this invention.

Fig. 1b is a diagrammatic representation of a system showing certainfundamental operations included in my invention.

Figure 1c is a pair of curves showing the relationship between aballistic correction and range for a predetermined point in space.

Fig. 2 is a perspective view of a system of cams t showing certainfundamentals of operation of a gunfire control system.

Fig. 3 is a schematic showing of the gunfire control system showing howcorrections for time of night of the projectile are introduced indetermining lead angle in a follow-up system insofar as the elevationmovements of the gun are concerned. The system is not a complete one andis merely shown to simplify the explanation A of the complete system asrepresented in Fig. 5.

Fig. 4 is a schematic showing control system showing how correction fortime of night of the projectile are introduced in determining lead anglein a follow-up system nsofar as the azimuth movements of the gun areconcerned, but which, like Fig. 3, is also incomplete.

Fig. 5 is a schematic showing of a complete system by which the systemsshown in Fig. 3 and Fig. 4 are combined, together with additional errorcompensating features, so that the system will automatically provideballistic corrections for time of night of the `bullet inl lead angledeterminations, corrections for air speed, and corrections for altitude.

Fig. 6 is a schematic showing of the control system for the drivingmotors.

Fig. 7 is an enlarged side view of the cams shown in Figs. 4 and 5.

It is well known that ballistic errors of a gun fired from a high speedairplane vary widely depending upon the direction of nre. These largeerrors are due to various factors, the important ones consisting ofrelatively into which the shot is nred with a resulting enect on thespin of thebullet due to the riningA and to the fact that the actualnight is not directly in line with the surrounding air. To compensatefor the ballistic errors introduced by the high air speed into which theprojectile is fired, the gun must be displaced relatively to the sightin order that the relatively moving air vwill not, in eiect, cause theprojectileto deviate from its course of travel toward the target. In thecase of the gunnre high wind velocity displacement of the gun withrespect to the sight will vary in a manner dependent upon the positionwhich the sight occupies with respect to the plane, the position of thesight being determined by the position of the target. In this respect,it will be apparent that a dierent displacement of the gun will berequired in the case where the sight is pointed in an upward directionwith respect to a horizontal plane than will be had in the case wherethe sight is point-ed downwardly with respect to a horizontal plane.Likewise, it will be apparent that different deflections wi11 berequired dependent on whether the projectile is fired with or against;the wind. Assuming that the airplane mounting the gun is operating at aconstant speed and at a constant elevation, and that the target isflying at the same speed at a constant range with respect to the planecarrying the gun, the ballistic errors vary with the air speed and it ispossible to figure out by complicated ballistic formulae both theazimuthal or lateral deflection of the gun and the vertical orelevational deflection of the gun with respect to the sight required tointroduce the proper ballistic corrections when the target is at anypoint on a sphere measured by the range of the target from the gun.Assuming that al1 other factors remain constant and that a change inrange only takes place, it will be apparent that a change in deflectionmust be had to compensate for the change in range. As pointed out, thesecalculations are based on the assumption of a constant elevation andidentical air speeds of both the target and the gun. Obviously, changingconditions in an airplane are too rapid to permit the manual calculationor introduction of the required deflections into a driving systemintermediate the gun and its sight.

As pointed out above, one of the principal objects of this invention isto provide mechanism for automatically introducing the required lateraland vertica1 deflections into the control mechanism intermediate thesight and gun. This is accomplished by means of an arrangement of camswhich are rotated with movement of the sight and gun in azimuth andmoved back and forth with vertical or elevation movement of the gun andsight in a manner to be described.

I have found that the ballistic errors or required deflection of the gunwith respect to the sight in both azimuth and elevation can be expressedmathematically as X-l-AY, where X is a function of both azimuth andelevation, Y is a different function of azimuth and elevation and A is afunction of range. The application of this mathematical expression inthe gunfire control system to be hereinafter described will be bestunderstood upon brief reference to the subject of ballistics. Exhaustivetests have been conducted on various projectiles and from these testsaccurate ballistic data regarding the path of flight of a givenprojectile have been obtained. As a result the trajectory of a givenprojectile for all angles of azimuth and elevation in the sphere ofgunfire with respect to relative wind for velocities thereof varyingfrom zero to fairly high values are known. For the specific projectileto be fired from the gun to be controlled by the hereinafter describedmechanism it was noted that Within the first one hundred yards or so ofprojectile flight a certain deflection occurred. This deflectioncomprises two components one vertical or elevational and one lateral orazimuthal, each of which is designated X. This initial deflection isdifferent for different positions of the gun in azimuth and elevationwith respect to the relative wind direction. However, the X component ofdeflection remains relatively constant for all working ranges to whichthe projectile travels, even though as the range becomes larger anothercomponent Y which varies with range is added. The deflection Y occurringbeyond the first one hundred yards or so of projectile flight alsovaries with azimuth and elevation positions of the gun with respect tothe relative wind direction. This latter deflection is made up of theoriginal constant X component plus the value of Y for the particularrange at which the deflection is measured. The projectile deflection ineach of the lateral and vertical directions beyond that of thedeflection X is designated Y. Hence, X-l-Y represents the totalcomponent of deflection of the projectile either laterally or verticallyfor some predetermined range. Ballistic data obtainable furtherindicates the value of Y for variations in range. Thus, for example, ifthe value of Y at say 600 yards were known the value of Y at less than600 yards would be some value less than the value of Y at 600 yards andfor ranges of more than 600 yards the values of Y would be greater thanthe value of Y at 600 yards. All of the foregoing, of course, is basedupon constant azimuth and elevation position of the gun with respect toa relative Wind of constant velocity. It was thus observed that a valueof Y for some particular range may be selected, for example, 600 yards,and that by multiplying this value of Y by a factor, such as A, which isa function of a known range, the value of Y for that particular rangewas obtainable. Thus at 600 yards, for the as sumed conditions, thevalue of A would be unity, for ranges less than 600 yards the value of Ais less than unity and the value of A at ranges greater than 600 yardsis greater than unity. The mathematical expression is now, therefore,written as X +AY in which X is a substantially constant function ofazimuth and elevation A is a function of range and Y is a differentfunction of azimuth and elevation.

The foregoing discussion of the significance of X -l-AY may best beunderstood upon referring to the three coordinate vector diagram (Fig.1a) which illustrates the projectile path to two target positions in thesphere of gun-fire for a projectile fired from a gun mounted on anairplane. In this illustration specific conditions are assumed insofaras airspeed, altitude and target position, velocity and direction withrespect to the airplane on which the gun is mounted, are concerned. Thetarget velocities as vectorially indicated are identical with each otherand are identical to that of the plane. Azimuthal angular gun positionsare defined by an angle 9 measured in the horizontal plane defined bythe axes H and H1 intersecting at point O, with that portion of the Haxis to the left of point O in the direction of flight of the plane asthe line of zero reference. Vertical or elevational angles of the gunare defined by an angle 4 and measured about point O in a plane verticalto the horizontal plane HH' having the portion of the vertical axis Vabove the point O as the line of zero reference. 'I'he various otherreference characters will be understood with the description of thisfigure. It will be noted that the angles a and o as Well as the variousother reference characters are provided with subscripts. This is for thepurpose of differentiating one target from the other later in thisdisclosure. However. for the purpose of describing this figure suchsubscripts will not be employed since the general description appliesequally to both targets. Thus, for example, when R is referred to bothof the targets R1 and R2 are referred to, etc.

The paths of two projectiles to two different points in the sphere ofgunre are indicated by the curved dotted lines OB. This sphere ofgunfire is of a diameter which varies with the range of the target andis defined by the azimuth angle 6, the vertical or elevational angle qand .the range OR to the target R.

DR is the vertical component of the projectile deflection at point R andis perpendicular to the line OR which is the line of sight to the targetR from point O and lies in the plane dened by the angle CR is thelateral component of the projectile deflection at point R and isperpendicular to both OR and DR. Assuming now that the projectiletrajectory is projected into the plane defined by the points OCR it willbe noted that the lateral component of the total deflection may bedetermined at any point along OR up to R. Thus the values of CR for allvalues of OR are determined. In the same manner the projectiletrajectory may be projected into the plane defined by the points ODR andthe values for DR for all values of OR determined. Each of thecomponents CR and DR comprises the X and Y values giving the totallateral and vertical components of deflection each as X|-Y. Thus X+Y=CRand X-j-Y=DR. The X and Y values comprising the lateral and verticalcomponents of deflection may not be the same, that is, the value of Xand Y in a lateral direction may not be the same `as the values of X andY in the vertical direction. The values of X and Y will further besubject to wide variation by the different positionsI of the gun inazimuth and elevation with respect to the relative wind. The X values ofdeflection represent the initial deflections of the projectile uponleaving the gun which thereafter remains stantally constant with rangeand the Y values represent the additiona1 deflection of the projectilecaused by the changing range during the course of the projectiles traveltowards the target.

As previously mentioned and as may be readily observed from the vectordiagram the values of Y both laterally and vertically vary with therange of the target, for an assumed constant angular gun position withrespect to a relative wind of constant velocity, In order to simplifythe design of the cams and the mechanism associated therewith from whichthe Y values are to be taken, a value of Y is selected which may applyonly, for example, at a range of say 600 yards for a particular angulargun position and wind velocity. The value of Y taken from the cam istherefore accurate only for a target range of 600 yards and fordifferent ranges must be modied by the factor A which is a function ofange. Thus the factor A is introduced into the mathematical expression X-l-AY. The lateral component of the deflection is plotted against OR asan abscissa as shown in Fig. 1c for the infinite number of points whoseangular position in the sphere of gunfire are controlled byV 0, and thevelocity of the relative wind. The two curves shown in this figure arethe result of such a plot for 01:90", 1=0 and 02:'225" and z=45 for aparticularly indicated airspeed of 250 M. P. H. and an altitude offlight of 15,000 ft.

The value of A depends only on range and for ranges of 200, 400, 600,800 and 1000 yards A respectively equals .18, .58, 1.00, 1.44 and 1.9.If these values are plotted they give a smooth curve showing that'A is afunction of range. The two solid curves on'Fig. 1c indicatey the lateralcomponent of the projectile deflection plotted from actual ballisticdata and it will be noted that each of the dotted curves obtained fromthe application of the expression X-l-AY agrees exactly with the relatedsolid curve except for the smalley,` ranges of from 0 to about 300 yardsand even here the error is slight.

The method of using the known ballistic data from which the curves wereplotted to find X1 and Y1 which are functions only of 0=90, =0 and thevalues of X2 and Y2 which are functions only of 0=225 and =45 is asfollows:

For 0=90, =0 the values obtained from ballistic data of the lateralcomponent of deflection at '200, 400, 600, 800 and 1000 yards arerespectively '7.3, 14.4, 21.4, 28.5 and 35.8. For 600 yards and 1000yards the expression X -l-AY can then be written:

Solving this expression there is obtained Xi=5.4 and Y1=16.0 for thespecified conditions.

Similarly for the angular position in the sphere 0:225" and @L -45 fromknown ballistic data there is obtained X2=4.8 and Yz=l0.3. X-i-Y valuesare then used in conjunction with the As of desired values of range, andthe points thus found connected to form the plots of Fig. 1c. Plots ofthe vertical components of deflection may be obtained in the samemanner.

From the foregoing it is readily apparentthat the expression X +AYrepresents either the lateral or vertical component of projectiledeflection and that the vectorial addition of X-i-AY for the verticalcomponent of deflection and X-i-AY for the lateral component ofdeflection gives the total deflection of the projectile and thus theamount of correction necessary to obtain a direct hit on the target. Ithas also been shown by the curves of Fig. 1c that the expression X-j-AYis correct insofar as the ballistics of the projectile are concernedsince the only deviation from the plot of the actual ballistic curvesoccurs at short ranges where such errors are negligible. Any point onsuch curves such as P is a func-tion of X-l-AY. The values of X arerelatively small as will be noted from Fig. 1c. If the error representedby X is considered negligible, the X cams may be omitted from the systemleaving only the Y cams.

For other points in space or on a sphere for a predetermined range,different curves of de. ection would be obtained instead of thoseillustrated, because each point on the curves is iniluenced by twofactors, namely, azimuth and elevation of the gun position with respectto the relative wind.

' The mathematical expression. X-l-AY greatly simplifies the knownformulae'for obtaining or calculating the trajectory of a projectile. Byernploying such an expression for each of the lateral and vertical'components of deflection to obtain the value of thetotal deection themechanics of the apparatus which is used to correct the position of thegun is greatly simplied thereby inherently increasing the overallaccuracy of such a device. i

These As noted in applicants statement of objects a system of threedimensional cams is provided which cams are moved lengthwise and rotatedin two directions and the surfaces thereof traced by suitable camtracers or followers. The cams are adjustable lengthwise in response tovarying gun elevation angles and rotatable in response to varyingazimuth gun positions. In one embodiment of this invention the cams maybe located in side-by-side relationship, one cam being assigned the Xvalues and the other cam being assigned the Y values for differentangular positions of the gun. Each of the abovementioned cam followersor tracers is provided with a pivotal link which at one extremity isconnected to the cam follower and is pivotally moved by the verticalmovements of its cam follower following the cam surface. 'I'he otherextremities of the links are connected together by another link themovement which at its centermost or some other predetermined positionindicates respectively the total vertical movement or the desired totalvertical movement of the two cam followers and hence indicates the X +Yvalue for the particular cam settings in azimuth and elevation, withrespect to a known value of relative wind. To modify the value of Y bythe factor A which is the function of range the pivot of the linkconnected to the cam follower scanning the Y cam is made adjustable.Thus for increasing ranges this pivot can be moved towards the camfollower thus increasing the transmission ratio of the link andincreasing the value of Y taken therefrom and with decreasing ranges thepivot is moved away from the cam follower to decrease the transmissionratio of the link and thereby the value of Y taken therefrom. Hence theassembly indicates X +AY for a given azimuth and elevation position ofthe gun when aimed at a target at a known range. Assuming that theforegoing correction provides lateral cor.. rection of the gun positiona second set of two cams may now be provided to produce the verticalcorrection necessary. The function of this set of cams and associatedlinkages is identical to that of the foregoing set the only differencebeing that the vertical deflection is indicated. The

vectorial addition of the lateral and vertical components of the totaldeection thus obtained provides the total displacement of the gun inazimuth and elevation with respect to the line of sight to the targetand is accomplished by means of driving mechanism interconnecting theazimuth drive of the gun with the set of two cams providing the lateraldeflection values and by means of a driving mechanism interconnectingthe elevation drive of the gun with the set of two cams providing thevertical deflection values. Thus the vectorial addition of X-I-AY forlateral deflection and X-l-AY for vertical deection is accomplished inthe position of the gun and the total correction for projectiledeflection for given azimuth, elevation, and range of the target withrespect to a known velocity and direction of relative wind is provided.

The above mentioned means by which this mathematical expression canreadily be carried out mechanically is indicated by Figure 1b. Fig. 1bshows two three-dimensional cams I and 2 both rotated with azimuthmovement of the gun and both move parallel to their axis with elevationmovement of the guns. The cams I and 2 are so constructed that withchanges of the position of the target in elevation only. thelongitudinal movement thereof will change the X and Y values. and such Xand Y values will likewise .be changed by rotation of the cams withchanges of the position of the target in azimuth only. Therefore, forany particular elevation, a. complete circle of azimuth values can beestablished by cam followers 3 and l (shown in top view). Therefore,these two three-dimensional cams can represent the functions for X and Yover the entire sphere by introducing the factor A of range as will beseen. Values proportional to X and Y can be taken from the cam followersor tracers 3 and 4 through levers pivoted at points indicated as X1 andY1 and taken off at point P, the Y value being taken from cam I and theX value being taken from cam 2. The variation of A for securingdifferent ranges can be obtained by shifting the position of the fulcrumY1, thereby introducing the proper multiplyng factor for the Y value.Therefore, Fig. 1 indicates a means of evaluating the ballistic errorsfor the entire sphere and for ranges (radii of the sphere) as fixed bythe travel of the fulcrum at Y1.

It will be noted that cams I and 2 must be shaped in accordance withprecalculated data. For instance, if these cams are to be indicative ofballistic errors, it will be necessary to take some predetermined testdata of such errors to dene at least two points on the curve X-I-AY. Thecurve may then be completed as a function of X-f-AY and the cams shapedaccordingly. Fig. 1b shows the calibration in degrees of cam I. The camsmay be calibrated from zero degrees to degrees. In some instances acomplete circle or sphere or values is not available for the gun forexample, as in the case where it is desired to shoot directly in avertically upward or downward direction, because of the azimuthballistic correction approaches 180 in value which is too large to bepractical. Collar portions at the ends of the cams as shown in Fig. 1bmay be provided to continue the same correction as the 0 or 180 value isapproached. In such instances calibrations may be made for a range lessthan 180 degrees, say, between 221/2 degrees and 1571/2 degrees. Thecams may be blanked along portions corresponding to points in space inwhich the airplane structure presents an obstruction to the gun.

Azimuth is measured such that zero azimuth will be in the direction ofthe propeller that is the line of ight of the airplane and elevation ismeasured such that zero elevation will be in a vertically upwarddirection in the airplane.

Assuming that the target occupies a certain position with respect to theplane, the sight will be pointed at the target and will occupy aposition with respect to the plane dependent upon the position of thetarget. Assuming further that the sight occupies a position pointing ata target located at 0 elevation and 90 azimuth with respect to the planein accordance with the corresponding curve of Fig. 1c, the value of Xmay be taken from cam 2, and the value of Y taken from cam I. Theposition of the pivot Y1 gives the proper multiplying factor A for thevalue Y. The values X and AY may'then be taken from the point P.Assuming that all other factors remain equal and that only a change inrange takes place, no movement will be imparted to either of the cams Iand 2, and the values of X and Y will remain the same. However, thechange in the range will change the value of A by changing the pivot Y1and, therefore, alter the value of AY. If under these conditions therange is changed from '100 yards, as shown in Fig.'1c on the curve forelevation and 90 azimuth, to 1000 yards, the value oi' A will changesufficiently to change the total of X-I-AY from 25 to 35.8 milsdeflection in a lateral direction.

It will be noted that the arrangement shown in Fig. 1b will be accuratefor only one speed of operation of the airplane. In order to make thesystem adjustable for different speeds, it is necessary to duplicate thesystem shown in-Fig. 1b and to interconnect the two points P thusobtained by a link which is adjustably fastened along two links eachsuch as link 6.

For certain velocities, for instance 150 to 350 miles an hour, thevalues of A which aiect the fulcrum of Y1 are the same Yfor all speeds.Therefore, when setting the value of A for a particular range, both Y1and Y2 will have identical settings. In order to simplify the mechanicsof the combination, I propose putting the two Y branches side by side sothat their fulcrums can be moved simultaneously and the same amount forrange, thus simultaneously changing the value of A for both links. Theend link from which the resultant X and Y values are taken will moveover the range of YiYz to XiXz.

The above arrangement is shown in detail in Fig. 2. A gun 8 is supportedfor vertical (i. e., elevation) movement and for horizontal (i. e.,azimuth) movement as will be readily apparent from the mechanicalstructure shown in the gure. A flexible cord 1 is trained about a systemof pulleys so as to allow either type of movement. When the gun moves inazimuth the r0- tation of gear 8 about a rotatable gear 9 will effect adrive through a. system of beveled gears which, in turn, will rotateshaft I0 in accordance with the azimuth movement of the gun. In a likemanner, when the gun is moved in elevation (by means not shown), gear IIwill rotate and drive a system of beveled gears which will, in turn,rotate a shaft I2, which shaft will drive a pair of rack and pinioncombinations so as to effect reciprocal movement of the framework I3,which reciprocal movement will be in proportion to the elevationmovements of the gun. A set of cams are pivotally mounted on theframework I3. In addition to cams I and2, which are suitable for aparticular speed of operation,

say, 350 miles per hour, there are provided, in'

addition, cams Ia and 2a which correspond to a different speed ofoperation', say, 150 miles per hour. Likewise, in addition to the camfollowers 3 and 4 there are provided similar cam followers 3a and 4acorresponding to the different speed. The arrangement is such that theadjustable pivots Y1 and Y2 for the two systems are arranged side byside, and the fixed pivots X1 and X2 are likewise arranged side by side.Thus. by a suitable rack and pinion arrangement I4, which is preferablydriven by the range finder through a cam drive I5 (to be describedlater), pivot points Y1 and Y2 will be simultaneously movable alongslots formed in the lever arms which are pvoted at such points. LinksI6, I1, I8 and I8, each has one of its ends connected to an end of a camfollowing lever, and its other end to either of two slotted links and2|. Adjustable pivots 22 and 23 are arranged to slide in such slots byvirtue of the controlling movements of a rack and pinion 24 whichreciprocates slotted members 25 and 26 integrally secured thereto andthe pivot points 22 and 23.

The movements of rack and pinion 24 are preferably responsive to airspeed, or altitude, or both,

las will appear later. The adjustable pivots 2 and 23 are interconnectedby a linkage System 21 having avertical rack 28 integrally connectedthereto, which, in turn, imparts rotary movement to a pinion 29. Theamount of angular rotation of pinion 29 is a measure of the totalcorrection to be applied to the system as will appear hereinafter. termsof speed ranging from to 350 miles per hour. vThe offsetting of the balland socket joints I9a as shown allow a full'range of movements of pivots22 and 23, that is, allow movements to the extreme ends of the' slots inlinks.

20 and2l'.

By the above-described construction, the camsA I and la may cooperate oract individually to give the required Y values for any given speedintermediate the air speed for which the cam l is designed and the airspeed for which the cam Ia is designed. Likewise, the cams 2 and 2acooperate to give the required X values in the same manner. .Assumingthat the air speed is 350 M. P. H., the pivots 22 and 23 will bepositioned adjacent the links I6 and I8. Thus the pivots 22 and 23 willbe vertically moved only by the links I8 and I8 and will not be affectedby movements of the links I1 and I9. If the speed drops to 150 M. P. H.,the pivots are positioned adjacent the links I1 and I9, and the verticalmovement of pivots 22 and 23 will not be affected by the movements oflinks I6 and I8 but only by movements of the links I1 andrI9. For speedsintermediate 150 M. P. H. and 350 M. P. H., vertical movement of thepivots 22 and 23 will be an average function respectively of thevertical movements of the link pairs I6--I1 and Iii-I9. Accordingly, theAY value will be measured by the vertical movement of the pivot 22, andthe X value will be measured by the vertical movement of the pivot 23.\These values are added together by the link 21 and converted into arotary displacement of the segmental gear 29 to give the total lateraldeflection of the gun with respect to the sight. A

As will become apparent later, a second set of four cams similar tothose shown in Fig. 2 is provided for giving the vertical or elevationaldeflection of the gun with respect to the sight. Similarly, a third setis provided for giving time of flight corrections.

In order to make the principles of my invention more easilyun'derstandableI have shown in Fig. 3 a system for'applying ballisticcorreotions and proper lead angle corrections only insofar as elevationmovements of the gun are concerned. In Fig. 4 I have shown a similarsystem, that is, for interposing ballistic' corrections and lead anglecorrections, only insofar as azimuth movements of the gun are concerned.Neither Fig. 3 norFig, 4 in itself represents a complete system.However, Fig. 5 shows a complete system and shows how the systems inFigs. 3 and 4 can be combined. Fig. 5 also shows, in addition, otherfeatures as will appear hereinafter.

When firing at moving targets, that is, moving relative to the night ofthe gun, it becomesV necessary to introduce a lead angle to the gunposition. The lead angle is measured by the product of angular velocityof the sight and the total time of flight of the projectile red and maybe either positive or negative, dependingupon whether the target isflying faster than the gun,

or whether it is flying slower than the gun.

Fig. 3 shows a system for introducing the proper Links 20 and 2I may becalibrated in l lead angle for the relative speeds of the guns andtargets. Such system includes a disk 30 driven proportional to theangular speed of the sight 3| (mounted on a pedestal 32) through asystem of gears 33 and 34. A ball assembly drive 35 is adjustableradially of the disk by virtue of a rack and pinion 36 such that theradial position of the ball assembly drive is xed by the particularrange through a suitable gear system including dinerentiai gear 31 whichis driven by a range finder (not shown). Cylinder 33 is driven in onedirection or another at variable speeds depending on the radial positionof ball assembly drive 36. The driven cylinder 39 drives one side of adifferential 40 through a slip clutch 4I i or centrifugal clutch ifdesired). The other side of dierential 46 is driven by a constant speedmotor 42 which drives a, disk 43, which, in turn, drives a variablespeed cylinder 44 through the ball assembly drive 45.

For any particular angular sight speed there is a position for the ballassembly 45 that will cause a diierential 40 to have zero rotation. Agyroscopic regulator 45 is driven by differential 40 through gear 41effecting a precessional movement of contact carrying arm 48, which isin proportion to the output rotation of the difierential. The gyroscopicregulator controls the speed and direction of the regulating motor 49 bythe contact relationship between contact carrying arm 48 and either ofcontacts 50 and 5I which energize the motor field windings 50a and a,respectively. The motor thereby drives an amount that is proportional tothe lead angle correction and will transfer such correction by its drivein to diiferential 52 by gears L53. This introduces into the drivingmechanism of the gun (i. e. the follow up mechanism between the sightand gun) the proper angle lead and at the same time puts the ballassembly drive 45 between the constant speed motor and the variablespeed substantially into such position that when the correct angle oflead is obtained the gyroscopic regulator will be in a balancedposition. It will be understood that if no correction were applied tothe system the sight 3| would drive the gun 54 directly throughdifferential 55 and exact follow up movements in elevation will beobtained. Elevation movements of the sight eiect rotation of the gearsystem 56 which will ultimately eiiect rotation of gear 66 and verticalmovement of link 65 to effect elevation movements ofthe gun. Gears 51,58, 59 and 60, each of which is rigidly secured to cams 6|, 62, 63, and64, respectively effect rotation of such cams, in response to azimuthmovements of the gun. Rotational movements of the gear 66 controllingthe gun elevation are transferred through the beveled gear assembly 61,through shaft 68 to rack and pinions 69 and 10. This will effect lateralmovements of framework 1| which carries the plurality of cams 6I to 64,inclusive, thereby effecting movement in the elevation direction oi suchcams to provide the necessary correction for the predetermined pointindicated 'by the sight in the sphere. It will thus be seen that theballistic correction for elevation movements of the gun will be impartedthrough a rack and pinion to shaft 12 in the form of an angular rotationthereof. This angular rotation is then fed through differential 52 todifferential 55 and thence through bevel gear assembly 56 to rotate gear66 thus causing an angular displacement of the gun in elevation relativeto the sight. The

rotation of the shaft 12 is indicative of a ballistic 12 correctionnecessary because of wind force and gravity, which correction takes intoaccount solely elevation movements of the gun.

The theoretical lead angle correction for any particular range is afunction ot the relative movement between the sight and target or, inother words, a function o1' velocity of movement of the sight as it isheld trained on e, moving target at a nxed distance. Since the disk 30rotates with an angular velocity in proportion to the velocity ofmovement of the sight, and since the radial position of ball assembly35, caused by the range finder is a function of range (also in dicativeof total time of ilight if the angular position at which the projectileis projected into the relative wind is known), the product of angularvelocity and total time of night in the drive results in a rotation ofcylinder 33 through an angular value which is indicative of thetheoretical lead angle. The range ilnder itself would impose on thedifferential 31 a rotation which is merely indicative of the theoreticaltime of night. Actually the time of flight would be different fordifferent directions of the sight of the gun in its movement within asphere. The assembly including cams 63 and 64 is effective to give anangular rotation of shaft 13 which .is indicative of a variation fromthe theoretical time of night for each point in space, that is, lforeach point having a particular azimuth elevation as well as range. Inother words, the rotation of shaft 13 is indicative of the correction tobe applied to the range finder indication in order to give the true timeof flight movement to ball assembly 35. The variations or loss in timeof flight for different directions in the sphere also nt the expressionX+AY where X, Y and A are similar functions as described in connectionwith the ballistic errors. Thus the design of the time of night cams maybe based upon obtainable ballistic data so that proper correction valuesare obtained therefrom for correcting the position of the ball assembly35 as determined` by range whereby the correct lead angle in elevationfor a particular target position and velocity is obtained.

The showing of Fig. 3 is for only one speed of operation of aplane-mounting gun and for giving the required deflection of the gunwith respect to the sight in a single direction, namely, elevation. Inthis showing, the cams 6I and 62 may correspond to either the cams I and2 or the cams la and 2a of Fig. 2 where such cams are constructed togive the vertical ballistic correction. The cams 63 and 64 give therequired time of flight correction which is used with the correctionrequired by range and by the speed of angular movement of the sight tosecure the proper lead angle. In this arrangement, the cams 6| and 62give the theoretical vertical ballistic correction which is fed into themechanical dierential 52. Ihe time of flight correction is fed into themechanical differential 31 with the necessary range correction forimparting movement to the ball assembly 35. Vertical movement of thesight 3|, as explained above, rotates the disc 30 which rotation throughthe speed-matched cylinders 39 and 44, together with the differential40, and gyro control 48 is effective through proportional movement ofthe ball assembly 45 to introduce the proper vertical correction to thedifferential 52. This correction is added to the theoretical verticalballistic correction and introduced into the diierential 55. The totalcorrection is thus mechanically intro- 4and time of flight cams.

aman? duced by the Iments of the cycler 15, thereby ultimately drivingshaft 11, first in one direction and then anby the speed of movement ofthe sight and the l time of flight correction.

It will be noted that the time of flight correction of the cams 63 and64 which is fed into the differential 31 for imparting a true time offlight movement to the ball assembly 35 is not effective to introduce alead angle correction unless accompanied by a movement of the sight. Inother words, the sight must first rotate the disc 38 in order that thedifferential 40 will B'veffective through the gyro control 48 to impartmovement to the assembly 45 to angle correction.

Fig. 4 shows a system by which angular` lead corrections are introducedfor azimuth movements only of the gun. Most of the structure shown is aduplication of the structure shown in Fig. 3 and is represented by thesame reference numerals. Hence, detailed description is deemedunnecessary. The outstanding difference is that the sight 3| drivesthrough differential gear 55 and gear 56a to rotate the gun in azimuthinstead of in elevation, as shown in Fig. 3. Another outstandingdifference is that an automatic cycler has been added. Lead anglecorrections are introduced through shaft 84 into the drive between thesight and the gun so `as to effect slight departure from exact follow-upof the gun as a consequence of azimuth movements of the sight. Theshowing of Fig. 4 is similar to that of Fig. 3, except that the leadangle correction is for lateral or azimuthal deflection instead of forvertical or elevational deflection In this showing, the cams 8| and 82may correspond to either the cams l and 2 or the cams la and 2a of Fig.2, the correction being for a single speed of operation. It will also benoted that this showing illustrates the manner in which the time offlight correction is added to the range adjustment to give thecorrection for loss of speed of the projectile which is equivalent to atheoretical increase in range. This latter feature is had by cooperationof the mechanical differentials 38 and 31. The range finder will firstoperate the differential 38 to vary the pivots 19 and 80 to introducethe proper multiplying factor A for the Y values obtained from theazimuth The time of flight correction is taken off the shaft 13 and fedinto the differential 31. Movement of the differential 31 is effectiveto impart movement to the ball assembly 35 Which, together with rotationof the disc 38, is effective to introduce the proper lateral lead anglecorrection into the differential 52.

Often times it is desirable to avoid having the gun maintain a fixedaimed position at a target when a number of shots are to be fired. Inorder to avoid the possibility of shooting projectiles at a particularspot when it may happen to be slightly oi the target and may resultl incompletely missing of the target, it is often desirable to effect aslight vibratory movement of the gun to spread or spray the shotsthrough a given area so that the possibility of one or more hits isconsiderably increased. In order to effect such spraying of the shotsfired, I have provided and introduced an automatic cycler 15 whichis-driven by motor 42. If the motor 42 rotates it effects reintroducethe proper lead other. This vibratory movement of shaft 11 is introducedinto differential 38 by the element 38a thereof and transmitted to shaft18. By a suitable drive, as shown, this vibratory motion will cause a4vibratory motion -of the adjustable pivot points 19 and 88 as indicatedby the arrows. Such drive includes a pair of cams.. such as, 8| and Bla,the construction ofwhich is shown enlarged and in detail in Figure 7;namely as comprising a pair of flexible ribbons 82 and 83 which areaxially offset with respect to each other and each of which has one endanchored on one cam and the other end anchored on the other as shown inFig. 7. The purpose of this'arrangement is to obtain a curvilinearinstead of a straight line relation between the rotative moveinder 44 ofFigs. 3 and 4) instead of using two.'

motors for effecting the same purpose. A simpler regulator circuit isshown, namely, one in which the gyroscope is omitted. Instead ofdepending upon the processional movement `of a 1 gyroscope, contactcarrying arms 88 and 89 are driven directly by the movement of thesight. The system in Fig. 5, in addition to providing for correctionsnoted in Figs. 3 and 4, provides for variable speed adjustment in themanner shown in Fig. 2. In other words, each unit of the four cams is ofthe type shown in Fig. 2, one set of four designating azimuth, the otherset of four, elevation corrections, and the third set of four, time ofight corrections. Each unit in itself, however, includes the additionalcorrection for variations in speed over a range, say, for example, frommiles per hour to 350 miles per hour. A long rack 98 which may bemanually slidable by rotation of pinion 9| is effective to adjust thepivot points from 92 to 91, inclusive, the details of which are shownmore clearly in Fig. 2 for a single unit. If desirable, pinion 9| may beconnected to the air-speed or air-flow dial so that the pivots willslide automatically in accord- I ance with speed of the plane. Tocorrect for altitude, an altitude dial 98 is made to rotate to aposition corresponding to the altitude at which the plane operates,thereby introducing a rotative movement to the differential 99 whichwill modify the air speed rotation of pinion 9|. The reason that airspeed and altitude can be lcornbined lthis way into a single correctionis that they are effected by the same phenomena, par-l It will befurther noted that each set of cams is provided with two X cams and twoY cams, each pair of cams respectively corresponding to the upper andlower speed limits by which appropriate X and Y values may be taken offand aidded together to give the required deflection for a selected airspeed.

In the operation of the apparatus shown in Fig. 5, the rack 90 is firstadjusted by the air speed through the differential 99 to position thepivot points 92 through 91 in the same manner that the pivot points 22and 23 of Fig. 2 are adjusted in order that the proper X and Y valuesfor the air speed will be had. The differential 99 will also be adjustedby the dial 98 to introduce the proper correction for altitude, thealtitude correction being a function of air density and, therefore,correctable or variable in termsr of air speed. The range finder throughthe differential 38 and cams 8| is made to adjust the pivot points forthe Y cams and thereby alter the AY values which are taken off at thepoints 92, 94 and 96. After these corrections are made, the segmentalracks 29a, 29h and 29e will respectively function to give thetheoretical, lateral, vertical and time of fiight ballistic corrections.The lateral ballistic correction from the rack 29a is taken ofi throughthe shaft 290a and the corrections provided by the racks 29h and 29e aresimilarly taken off through the shafts 29017 and 290e.

In the event that the target is not moving relative to the gun, thecorrections taken off through the shafts 290:1 and 290b represent thetotal lateral and vertical deiiections to be introduced intermediatesight and the gun. However, in the event that the target is movingrelatively to the gun, it is necessary to introduce a lead anglecorrection as explained above. This is done through the rack 29e and theshaft 290e which feeds the time of iiight correction into thedifferential 31 where it is differentially added to the movementimparted to the differential 31 by the differential 38 as controlled bythe range finder. The differential 31, as explained in connection withFigs. 3 and 4, functions to position the parts 35a and 35h whichcorresponds respectively to the part 35 in Fig. 4 and the part 35 inFig, 3.

The setting of the part 35a does not effect the azimuth` or lateralballistic correction unless the target is moving relatively to the gunin azimuth. In the event that the target is moving relatively to the gunin azimuth, a movement will be imparted to the part 45a proportional tothe velocity of relative movement in the same manner that the part 45 inFig. 4 is moved. This movement is taken off through the shaft 29|a andrepresents the azimuth lead angle correction which is added to thelateral or azimuth ballistic correction by the differential 292a. Thetotal correction from the differential 292a is transmitted through theshaft 293a to the differential 294a where it is introduced into thedrive intermediate the sight 3| and the gun. Except for the correctionintroduced in the differential 294a, the gun would be moved by the shaft295a so as to exactly follow the movement of the sight 3| in azimuth.Movement of the shaft 295a therefore represents the sum of movement ofthe sight 3| in azimuth and the total azimuth or lateral ballisticcorrections.

The parts 35h and 45h function similarly to the parts 35a and 45a inintroducing an elevational or vertical lead angle direction in the eventthat the target is moving relative to the gun in a vertical direction.Movement of the part 45h is taken on! through the shaft 29|b andrepresents the vertical lead angle correction. This correction isintroduced into the differential 2921: where it is added to thetheoretical vertical ballistic correction providedby the rack 29h andshaft 290b. The total vertical correction is then transmitted throughthe shaft 2931 to the differential 294b where the corrective value isdifferentially added to the vertical movement of the sight 3|. Thedifferential 294b thus causes, through the shaft 295b, the gun to bemoved to a position having the proper amount of vertical deflection withrespect to the sight 3 I.

Instead of having the sight 3| drive the gun directly, which wouldrequire considerable force, it is possible to have the sight operate aregulator which will control a power amplifying means which will in turndrive the gun. Going a step further, it is also possible to have a pilothandle, such as 00, operate a plurality of Silverstats (i. e. variableresistor units) which will control the energization of the fieldwindings of train and elevation driving motors 0| and 02 of Fig. 5, inthe manner more clearly shown in Fig. 6. Four Silverstat units |03, |04,|05 and |06 are provided in circuit with the field windings of motors|0| and |02. The handle |00 has four spider arms |03a, |04a, |05a and|06a projecting therefrom which are preferably slightly resilient, orbetter still, which have ball and socket joints with the handle in orderto permit slight rotative movements thereof relative to the handle. Itwill be obvious that as the handle is moved upwardly, it effectsenergization of one field winding only, of motor |02 to drive the motorin one direction; and if it is moved downwardly, it will effectenergization of the other field winding of motor |02, and that thenumber of Silverstat contact arms shunted or the amount of resistanceshunted is in proportion to the amount of upward or downward movement.Inasmuch as handle |00 is pivotally mounted on wheel |01, the control ofthe sight and gun by the operator is facilitated because the operatorwill have the feeling that he is manually moving sight 3| since handle00 follows the sight in both azimuth and elevation. The operator will beunaware that he is merely piloting the movement of the sight and gun bycontrolling a power amplifying circuit which includes motors |0| .and|02 which actually drive both the sight and the gun, as shown. Insteadof controlling motor field windings, the Silverstats could equally aswell control shunt field windings of a generator in a variable voltagesystem (not shown) in a manner well known in the art.

I am, of course, aware that others, particularly after having had the,benefit of the teachings of my invention, may devise other4 devicesembodying my invention, and I, therefore, do not wish to be limited tothe specific showings made in the drawings and the descriptivedisclosure hereinbefore made, but wish to be limited only by the scopeof the appended claims and such prior art that may be pertinent.

I claim as my invention: g

1. In a control for a system having a gun, a sight, and follow upmechanism for effecting movement of the gun in accordance with movementof the sight, error compensating means interposed in said follow upmechanism so as to introduce a deviation between gun and sight so thatsubstantial instead of exact follow up occurs, said error compensatingmeans including a pair of three dimensional cams each having a tracerassociated therewith, means responsive to movements of the gun inazimuth for rotating the cams, means responsive to movements of the gunin elevation for longitudinally moving the cams whereby said tracers aremoved, and means for adding the movements of said tracers whereby theerrors to be compensated for are indicated.

2. Apparatus as recited in claim 1 in which said adding means isrepresented by the curve X +Y where X and Y are each different functionsof azimuth and elevation and are represented by the two separate cams,one of said cams being shaped according to the X values and the other ofsaid cams being shaped according to the Y values.

3. Apparatus as recited in claim 1 in which said adding means includestwo levers, each having an end movable by the corresponding tracer andone of said levers having a movable pivot, and linkage means forinterconnecting the other ends of said levers, said adding means beingrepresented by the expression X+AY where X is indicative of any point onone cam and is indicative of a precalculated error which is a functionof azimuth and elevation for all points of a sphere as contained on onecam and Y is indicative of a precalculated error and is a differentfunction of azimuth and elevation for all points of a sphere of gunfireas contained on the other cam, and A is a function of range which may bemodified by moving said adjustable pivot point.

4. A gun fire control system comprising, in.'

combination, a sight, a gun, follow up mechanism for moving said gun inaccordance with movements of said sight, means for introducing gun firecorrections in the follow-up mechanism including a pair of threedimensional cams, means for rotating said cams about their axes inaccordance with azimuth movements of said gun, means for moving saidcams along their axes in accordance with elevation movements of saidgun, a tracer for each of said cams, which are biased into continuousengagement therewith and linkage means for interconnecting said tracersand for providing a corrective movement which is applied to saidfollow-up mechanism.

5. In a gun fire control system, apparatus for interposing a correctionto the position of a gun comprising, in combination, a pair of threedimensional cams, means for rotating said cams about their longitudinalaxes and means for propelling said cams along said axes, a followerassociated with each cam, linkage means interconnecting said followers,take-off means operated by said linkage means to give a movement whichis proportional to the summation of movements of both of said followers,and means for adjusting said take-off means along said linkage meansinterconnecting said followers,

6. Apparatus as recited in claim 1 in which said errors are ballisticerrors of the gun and in which each of the cams is so shaped as to beindicative of ballistic errors for substantially all points in a sphereof gunfire.

7. A gun fire control system comprising, in combination, a gun, a sight,piloting mechanism for effecting movement of the gun in space inaccordance with movements of said sight, means for introducing variabledeviations to the gun position which are different for different pointsof the sphere and which compensate for ballistic errors, said meanscomprising a pair of three dimensional cams which are each shaped inaccord-V ance with precalculated ballistic error data so 18 that foreach point in space of the gun there is a corresponding point on one camwhich is a function of azimuth and elevation and which is proportionalto the amount of required ballistic compensation of error for aparticular gun position, and there is a corresponding point on theotherrcam which is a different function of azimuth and elevation andlikewise proportional to the amount of required compensation of errorfor such particular gun position, and means for following the camsurface variation valong two dimensions of each of said cams, adding theresults and applying them to said -piloting mechanism, and means foradjustably modifying said last mentioned means in accordance with rangeof a target.

8. 'Apparatus as set forth in claim '7 in which each cam is providedwith a lever which is movable in proportion to the surface variations ofthe associated cam, one of said levers including an adjustable pivotwhich is adjustable in accordance with the range of the target and isincluded in the last mentioned means of claim '7 so that the totalballistic correction may be represented by the expression X-l-AY where Xand Y are different functions of azimuth and elevations forcorresponding points on each of said cams and A is a function of rangewhich is applied in the form of said adjustable pivot.

9. Apparatus as set forth in claim '7 together with a duplicate set ofcams and means for following the cam surfaces, which cams, however, areof different shapes .than the ballistics cams, being shaped inaccordance with precalculated data on time of flight cfa projectilefired, and means responsive to the velocity of movement of the sight asit is held on a moving target and to the range of the gun for adding alead angle correction to said ballistic correction so as to furthermodify the relative position in space of said sight and gun.

l0. Apparatus as set forth in claim 7 in which the gun and sight aremounted on a moving vehicle and which said compensating means in'-cludes a duplicate set of cams and means for following the cam surfaces,which cams, however, are of different shapes than the ballistic cams,being shaped in accordance with precalculated data on corrections fortime of flight of a projectile fired for different points in a sphere ofgunfire, and means responsive to the relative velocity of movement ofthe sight as it is held on a moving target and to therange of the gunfor adding or subtracting a lead angle correction to said ballisticcorrection so as to further modify the relative position in space ofsaid sight and gun, said last mentioned means being modified by saidduplicate set of cams so as to include compensations for errors due totime of flight determination.

11. Apparatus as recited in claim 1 in which said adding means isrepresented by the curve X-l-AY, where X and Y are different functionsof4 azimuth and elevation and are represented by the two separate camsand where A is a function of range of the gun, together with a duplicatepair of cams and an additional adding means which may be represented bythe curve Xi-l-AiYi, where X1 and Y1y are different functions of azimuthand elevation and are indicative-of the correction to be added becauseof differences in time of flight of the projectile for differentdirections of fire within a sphere, and means for totalling the effectsof both of said adding means so as to provide a corrective displacementof gun 19 with respect to the position in space of the sight so as tocompensate for both ballistic errors and errors due to variable time offlight of the projectile for different directions of fire.

12. In a gun re control system, a gun, a sight, gun position regulatingmeans including a differential gear for driving said gun in accordancewith movements of said sight, including rotatable means driven by saidsight, a second rotatable means, a constant speed motor and a variablespeed transmission for driving said second rotatable means, a regulator.,differential means operable in 'response to relative rotation betweensaid two rotatable means to control said regulator so as to vary thespeed ratio between said variable speed transmission so as to eifectspeed matching between said two rotatable means and to simultaneouslyintroduce in said position regulating means a lead angle displacement'so that only substantial and not exact follow up occurs between saidsight and gun.

13. Apparatus as set forth in claim 12 in which a variable speed driveis provided between said sight and said first mentioned rotatable meanswhich is varied in accordance with range as determined by a rangefinder.

14. Apparatus as set forth in claim 12 in which a variable speed driveis provided between said sight and said rst mentioned rotatable meanswhich is varied in accordance with range as determined by a range nderand means including a pair of three dimensional cams which are shaped inaccordance with time of flight corrections of a projectile and means forfollowing the cam surfaces in two directions and to add the effectsthereof and to interpose a time of flight correction between said sightand variable speed drive.

15. Apparatus as set forth in claim 12 in which a variable speed driveis provided between said sight and said first mentioned rotatable meanswhich is varied in accordance with range as determined by a range nderand means including a pair of three dimensional cams which are shaped inaccordance with time of flight corrections of a, projectile and meansfor following the surfaces of said cams in two directions and to add theeffects thereof and to interpose a time of night correction between saidsight and variable speed drive and a second pair of three dimensionalcams shaped in accordance with ballistic corrections for the gun,together withmeans for interposing said ballistic corrections to saiddiil'erential gear in the gun drive in order to effect a deviationbetween the sight and gun which is in proportion to the ballisticcorrection.

16. A gun fire control system comprising, in combination, a sight, agun, means for piloting the gun in accordance with movements of thesight, compensating means for introducing a displacement between saidsight and gun so that substantial instead of exact follow up occurstherebetween including means responsive to the velocity of movement ofthe sight for determining lead angle, said compensating means alsoincluding a device for compensating for ballistic errors of the gun inboth azimuth and elevation, "a, second device for compensating for timeof flight errors of a projectile iired by the gun in the determinationof lead angle, each of said devices including a pair of threedimensional cams, each pair being shaped in accordance withprecalculated values of ballistic errors and time of night errors,respectively, and means for tracing the 20 cam surfaces in both azimuthand elevation and for introducing adjustable values of range.

17. Apparatus as set forth in claim 16, in which both said devices areprovided with means for adjusting their output depending upon thevelocity of the relative wind.

18. Apparatus as set forth in claim 16, in which both said devices areprovided with means for adjusting their output depending upon thedensity of the air.

19. Apparatus as set forth in claim 16, in which both said devices areprovided with means for adjusting their output depending upon thevelocity of the relative wind and the density of the air.

20. In combination, a gun, a sight movable in azimuth and elevation forimparting similar movements to said gun, and means operated dependingupon movements of the sight for automatically displacing said gun inazimuth and elevation with respect to said sight to introduce azimuthand elevation projectile ballistic corrections according to theballistic characteristics of the projectile to be fired by said gundepending upon the particular position of said sight in azimuth andelevation with respect to the relative wind.

21. In combination, a gun, a sight movable in azimuth and elevation,follow-up mechanism for moving said gun in azimuth and elevation withsaid sight, and means for adjusting said mechanism as an automaticfunction of movement of the sight to displace said gun in azimuth andelevation with respect to said sight to introduce projectile ballisticcorrections according to the ballistic characteristics of the projectileto be fired by said gun for the particular position of the sight inazimuth and elevation with respect to the relative wind.

22. In combination, a gun, a sight movable in azimuthal and elevationaldirections, follow-up mechanism for moving said gun in accordancewith'movement of said sight, and camming means rotatable depending uponmovement of said sight in one of said directions and shiftable axiallydepending upon movement of said sight in the other of said directions,said camming means being operative to automatically introduce into saidfollow-up mechanism a projectile ballistic correction for apredetermined relative wind velocity depending upon the position of saidsight in azimuth and elevation, with respect to the relative wind,thereby displacing said gun with respect to said sight in at least oneof said directions.

23. In combination, a gun, a sight movable in azimuthal and elevationaldirections, follow-up mechanism for moving said gun in accordance withmovement ofsaid sight, and a pair of cams respectively rotatabledepending upon movement of said sight in one of said directions andshiftable axially depending upon movement of said sight in the other ofsaid directions, each of said cams having an element displaceablethereby, means adjustable according to range for varying thedisplacement of one of said elements in accordance with changes inrange, and means for adding the displacement of both of said elements tosecure a ballistic correction in one of said directions for apredetermined velocity of relative wind depending upon the position ofsaid sight in azimuth and elevation with respect to the relative wind,and means for introducing `said correction into said follow-up mechanismto displace said gun in at least one direction with respect to saidsight, movement of said cams depending upon movements of said sightbeing effective to con- 2l tinuously and automatically change said addeddisplacement and give the required projectile ballistic correction ofthe gun for all positions of said sight with respect to the relativewind.

24. Apparatus as claimed in claim 23 together with an additional pair ofcams for giving the required projectile ballistic correction for apredetermined velocity of relative wind different from the firstmentioned predetermined velocity of the relative wind, and meansinterconnecting said cams for giving the required projectile ballisticcorrections for velocities of the relative wind intermediate thepredetermined velocities.

25. Apparatus as claimed in claim 23 wherein said projectile ballisticcorrection is according to the expression X+AY, one of said cams beingshaped according to the X values of projectile deection. the other ofsaid cams being shaped according to the Y values of projectiledeflection, and said means adjustable according to range beingconstructed according to the A values which are functions of range.

26. In a control for a system having a gun, a sight, and follow-upmechanism for effecting movement of the gun depending upon movement ofthe sight, error compensating means interposed in said follow-upmechanism so as to introduce a deviation between the gun and sight sothat substantial instead oi' exact follow-up occurs, said errorcompensating means including a three dimensional cam dimensionedaccording to ballistii errors of the projectile to be fired by said gunand having a' cam follower associated therewith, means for rotating thecam depending upon movement of the sight in azimuth, means forlongitudinally moving the cam depending upon movement of the sight inelevation, means for producing a quantity indicative of movements of thecam follower, and means for varying said quantity independently of thecam follower.

27. In a device for controlling the movements of a gun depending uponmovements of a sight, the combination of means for producing aquaritityindicative of movements of said sight, means operated depending uponmovement of said sight for producing a quantity indicative of aballistic characteristic of the particular projectile to be red by saidgun, means for producing a quantity indicative of the velocity of therelative wind, means for modifying said quantity indicative of relativewind depending upon the density of the air, means for modifying saidquantity indicative of a ballistic characteristic of said bulletdepending upon the value of said last named modified quantity, and meansfor utilizing the resulting quantity in conjunction with said quantityindicative of movements of said sight to angularly position said gunwith respect to said sight.

JOHN F. PETERS. I

